Hydrolysis Of Soybean Protein By Aspergillus Oryzae Protease

Soybean fermentation food is a traditional food of China and East Asian countries with a long history. The protease by microorganisms decompose soybean into peptide and amino acid on fermentation process, it not only can improve the flavor of food, but also absorb and generate functional active substances to human. Aspergillus oryzae is the main strain on fermentation soy products, it produces rich hydrolase such as protease enzymes and polysaccharide enzymes. Protease system includes neutral protease, alkaline protease, acid protease, carboxypeptidase and aminopeptidase. As revealed the form of nutrition and flavor substances of polypeptides and amino acids in the fermentation process and optimization of A.oryzae protease lay the theoretical foundation.To select the fine strain of No.3 A.oryzae in soy sauce mash acts as experiment strain, and to optimize the triangle bottles(500 ml) solid state culture conditions through single factor experiment and orthogonal experiment. The result indicates that incubation temperature 35℃, spore inoculation 0.2%, the medium composition ratio of bran, flour, rice flour 7:2:1, bottle filling quantity of 25 g, incubation time 72 h, and in this condition, the spores and neutral protease activity are 14.83×109 per one gram and 22972U/g.Different concentrations of impact factors(Fe3+, Fe2+, Ca2+, Mn2+, Cu2+, Ge2+, EDTA, lauryl sodium sulfate, Ag+, Zn2+, etc.) effect on A.oryzae protease system, obtain a variety of protease system distribution of crude enzyme. Among them, influence factor played a positive role of carboxypeptidase, the strongest influence is Ca2+, the relative enzyme activity reached 300%; For acid protease, the strongest promotion effect is Mn2+, the relative enzyme activity reached 317%, the strongest inhibitory effect is lauryl sodium sulfate, the relative enzyme activity is live almost 0; influence factor played a negative role of neutral protease, alkaline protease and aminopeptidase, the strongest inhibition are Ge2+, Fe3+ and LDS, respectively, the relative enzyme activity was almost 0. There is a relationship between protease and hydrolysate. Among them, the strongest of hydrolysis free amino acid ability is protease with the treatment of Ag+, the weakest is Cu2+, the strongest of hydrolysis small peptide ability is protease with the treatment of Zn2+, the weakest is Ge2+, the greatest of degree of hydrolysis is protease with the treatment of Ca2+, the weakest is Fe3+. Through the sensitivity analysis, it found that the largest contribution about hydrolysing soybean protein is aminopeptidase, followed by the alkaline protease, the smallest is neutral protease. Therefore, we could act aminopeptidase as an important indicator of screening A.oryzae and evaluating koji.In order to further study the relationship between A.oryzae protease and hydrolysis of soybean protein, we use the artificial neural network model. The experiment selected 26 groups as the training group, 5 groups as predicting group, the predicting results of the content of free amino acid, content of small peptide, degree of hydrolysis are compared with the experimental results, the regression coefficient(R2) were 0.92, 0.88, 0.95. It shows that artificial neural network can effectively predict the hydrolysis soybean protein ability by protease.